issue15747.go

     1  // errorcheck -0 -live
     2  
     3  //go:build !goexperiment.cgocheck2
     4  
     5  // Copyright 2016 The Go Authors.  All rights reserved.
     6  // Use of this source code is governed by a BSD-style
     7  // license that can be found in the LICENSE file.
     8  
     9  // Issue 15747: liveness analysis was marking heap-escaped params live too much,
    10  // and worse was using the wrong bitmap bits to do so.
    11  
    12  package p
    13  
    14  var global *[]byte
    15  
    16  type Q struct{}
    17  
    18  type T struct{ M string }
    19  
    20  var b bool
    21  
    22  func f1(q *Q, xx []byte) interface{} { // ERROR "live at call to newobject: xx$" "live at entry to f1: xx$"
    23  	// xx was copied from the stack to the heap on the previous line:
    24  	// xx was live for the first two prints but then it switched to &xx
    25  	// being live. We should not see plain xx again.
    26  	if b {
    27  		global = &xx
    28  	}
    29  	xx, _, err := f2(xx, 5) // ERROR "live at call to f2: &xx$"
    30  	if err != nil {
    31  		return err
    32  	}
    33  	return nil
    34  }
    35  
    36  //go:noinline
    37  func f2(d []byte, n int) (odata, res []byte, e interface{}) { // ERROR "live at entry to f2: d$"
    38  	if n > len(d) {
    39  		return d, nil, &T{M: "hello"} // ERROR "live at call to newobject: d"
    40  	}
    41  	res = d[:n]
    42  	odata = d[n:]
    43  	return
    44  }
    45
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